There is a prevailing clinical impression that patients taking cyclosporine develop exaggerated Cushingoid changes if they are taking concomitant corticosteroid therapy. In this study we have investigated 4 groups of patients taking prednisolone and/or cyclosporine for inflammatory eye disease. All plasma prednisolone and cortisol levels have been measured. Initial protein binding studies with plasma proteins and in patient plasma, indicate the binding of prednisolone to be lower than observed in control plasma (f:0.74 vs. 0.79 at Cu greater than 200 ng/ml). Although levels of cortisol binding globulin indicate slight increase in 2 patients, no significant changes were observed whether cyclosporine was added to the regimen of patients on prednisolone or vice-versa. Slight decrease in binding (Approx. 5-10%) may enhance partitioning of prednisolone into tissues and may reflect clinical implications associated with steroid accumulation.